1. Field of the Invention
This invention relates in general to vehicle washing systems, and specifically relates to a vehicle rear surface washing system, comprising an apparatus for washing the vertical rear door of trucks, trailers, buses and vans.
2. Description of the Prior Art
Automated vehicle systems have been developed for cleaning large vehicles such as the vertical sides of the trailers of semi-trailers towed by tractors, whereby the driver pulls a trailer into the system until the side and rear surface of the trailer are located at a predetermined position, and the system is energized to begin the washing procedure. The vehicle washers usually are constructed with brushes for cleaning and sweeping the sides of a vehicle and one or more brushes adapted to sweep the rear of the vehicle as it passes through the washing system. Some of the vehicles have recessed, vertically movable rear doors while others have hinged doors that swing about vertical axes. Sometimes, a vehicle will have a step or loading ledge which protrudes outwardly beneath the rear door. The different configurations of the rear surfaces of the vehicles cause some of the cleaning systems to be ineffective since the brushes do not make proper contact with the surfaces that require cleaning. One conventional approach to rear door cleaning is to provide a signal to the driver to halt his vehicle at a predetermined point in the washing system so as to allow a vertically-disposed rotary brush to descend and sweep the rear door. In some instances drivers cannot stop their vehicles precisely when signalled and must either back up the vehicle to the predetermined point or have the rear door washed with insufficient brush contact to provide adequate cleaning.
Another approach to cleaning the rear surface of a vehicle is described in Griffiths, U.S. Pat. No. 2,610,342, where a rotary brush is horizontally mounted upon a pivoted, swinging mechanism, which is then mounted to a vertically moving carriage. When the vehicle has stopped within a predetermined range beyond the brush mechanism, the rotary brush frame pivots and swings outwardly from the vertical carriage and brushes the rear surface, held against the rear door by either a counterweighting action of the opposite end of the brush frame or by the torque of a motor which is used to pivot the rotary brush frame outwardly. The driver must stop the rear of the vehicle a short distance beyond the vertical carriage mechanism, so that the rear surface is not beyond the reach of the rotary brush when it is pivoted outwardly. With semi tractor-trailer vehicles, the problem is magnified due to the immense sizes and loaded weight of the trailers involved, so that it is difficult for a driver to position the rear end of the vehicle within the narrow range required by the washing apparatus. Moreover, the problem is complicated when the washing apparatus must handle vehicles of different lengths because any signal to a driver of a vehicle of a given length will not necessarily give a proper stop indication to a driver having a vehicle of a different length.
Another method for cleaning the rear surface of a vehicle is to employ vertical rotary brushes mounted at the end of vertically pivoting arms of fixed length to brush both the sides and rear of the vehicle. After the sides have been brushed, and as the rear of the vehicle passes by the brushes, the brushes and arms pivot and swing outwardly towards the rear surface and brush the rear surface. Because the brush is mounted on an arm of fixed length, the brush bristles cannot be maintained tangential to the rear surface as the arm pivots, and thus the velocity of the bristles changes as the brush moves across the rear surface. Consequently, this approach often results in uneven cleaning of the rear surface because of the changing velocity of the brush bristles at the point of contact with the rear surface.
Still another approach to cleaning vertical rear surfaces has been to employ a movable carriage which supports a horizontally-disposed brush for scrubbing the top and certain rear portions of a vehicle. In Thompson, U.S. Pat. No. 3,795,929, a carriage moves from the front to the rear of the vehicle as the horizontal brush scrubs the top; when the brush falls from the top of the vehicle, it actuates a control member which halts the carriage motion as the top brush cleans the rear window of upper rear vertical surface of the vehicle. However, this approach does not allow the cleaning of the entire vertical rear surface.